Re: The actual code of HHH

On 2025-02-26 21:52:31 +0000, joes said:

Since there is so much talk around, but not really about it,
let's take a look:
https://github.com/plolcott/x86utm/blob/
48b4cbfeb3f486507276a5fc4e9b10875ab24dbf/Halt7.c#L1081
In line 1137, we compute a flag:
u32 Root = Init_Halts_HH(&Aborted, &execution_trace, &decoded, &code_end,
(u32)P, &master_state, &slave_state, &slave_stack);
In line 918, we find it basically checks for the magic number
**execution_trace==0x90909090. What is this unexplained value?

The variable execution_trace is a pointer to a pointer to a 32 bit
unsigned int. The function Init_Halts_HH may update the pointer
*execution_trace or the number **execution_trace. The special value
0x90909090, when interpreted as a fragment of a program, means four
no operation instructions. That many no operation instructions is not
used in the compiled code so it can be used as a speial value where
otherwise instrunctions generated by the compiler are expected.
--
Mikko